1. Field of the Invention
The present invention relates to a method of die-casting of metals with dispersion of predetermined quantities of solid particles in the resulting metal castings. More particularly, in a preferred embodiment, the invention relates to hot-chamber die-casting of metals, such as magnesium alloys, with dispersion therein of precisely measured quantities of solid particles.
2. Brief Description of the Prior Art
It is already known that solid additives may be incorporated into the molten metal during die-casting. For example, Canadian Patent No. 953,078 of Aug. 20, 1974 discloses such a method where an additive is supplied into the sleeve through which the molten metal is injected and is pushed into the runner and the cavity by said molten metal. However, this arrangement, makes it difficult to achieve a good dispersion of a predetermined quantity of solid particles in the resulting metal casting because the solid particles introduced as disclosed in this Canadian patent cannot be readily maintained in one place to be quickly combined and intermixed with the molten metal, but are rather spread by gravity within the sleeve into which they are introduced and must travel some distance with the liquid metal through the sleeve, then through the runner and finally into the cavity. Thus, there are usually serious problems of segregation and non-uniformity of dispersion encountered in such cases.
U.S. Pat. No. 4,340,109 of Jul. 20, 1982 also discloses a similar arrangement where a predetermined amount of a preheated filler material, such as sand, is placed in the shot sleeve leading to the runner and the die cavity and also a predetermined amount of molten metal alloy is placed in the same shot sleeve following the filler material and both are then forced through the runner into the die cavity to form a casting with the particular filler material intermixed with the molten metal. This method is not easy to implement. For example, solid particulate material will not readily stay in a nice neat pile as shown in this U.S. Patent. Also, the molten metal is normally injected or poured from metal containers, rather than being placed in a predetermined quantity beside the solid particles. Thus, the same problems as already described with reference to Canadian Patent No. 953,078 will arise. Also, if the molten metal is a reactive metal, such as magnesium, it may violently react with the solid particles being dispersed, producing undesirable residues or reaction products. This often happens when ceramic materials are placed in contact with molten magnesium for a sufficient period of time.